Copper based alloys comprising Ni and Sn have received considerable attention in connection with the manufacture of articles which may be shaped as cast, hot worked, cold worked, or machined. An early line of development is represented by papers by E. M. Wise et al., "Strength and Aging Characteristics of the Nickle Bronzes", Trans. AIME, Institute of Metals Divsion, Vol. 3, pp. 218-243 (1934) and by T. E. Kihlgren, "Production and Properties of Age Hardenable Five Percent Nickel-Bronze Castings", Trans. AFA, Vol. 46, pp. 41-64 (1938) which disclose Cu-Ni-Sn alloys which are strong and hard and which are suitable for certain casting applications. Equilibrium phase diagrams of Cu-Ni-Sn alloys are shown by J. T. Eash, "Constitution of Copper-Nickel-Tin Alloys", Metals Handbook, America Society for Metals, 1939, pp. 1371-1373.
More Recently, Cu-Ni-Sn alloys have been investigated and developed which are strong yet ductile and which are suitable, e.g., in the manufacture of wire, wire connectors, and springs. In particular, U.S. Pat. No. 3,937,638, issued to J. T. Plewes on Feb. 10, 1976, discloses articles which are processed by homogenizing, cold working, and aging. High levels of strength and ductility are ascribed to an alloy having a spinodally decomposed structure in which decompositon products, customarily designated as alpha-1 and alpha-2, are dispersed on a submicroscipically fine scale, as discussed in the paper by L. H. Schwartz et al., "Spinodal Decomposition in a Cu-9 weight percent Ni-6 weight percent Sn alloy", Acta Metallurgica, Vol. 22, May 1974, pp. 601-609.
U.S. Pat. No. 4,052,204, issued to J. T. Plewes on Oct. 4, 1977, discloses copper based spinodal alloys having compositions which are processed in a fashion similar to that disclosed in above-cited U.S. Pat. No. 3,937,638, but which, in addition to Cu, Ni, and Sn, contain fourth elements such as Fe, Zn, Mn, Zr, Nb, Cr, Al, or Mg in amounts within specified limits. U.S. Pat. No. 4,090,890, issued to J. T. Plewes on May 23, 1978, discloses copper based spinodal alloys which have compositions similar to compositions of alloys disclosed in above-cited U.S. Pat. No. 3,937,638 and 4,052,204, but which are cold worked by more limited amounts of rolling so as to achieve essentially isotropic formability in the rolled product. Resulting strip material is particularly suited for applications which require sharp bending as, e.g., in the manufacture of clips and electrical connectors.
Among further aspects of Cu-Ni-Sn alloys and their processing are a warm working treatment as disclosed in U.S. Pat. No. 4,012,240, issued to R. A. Hinrichsen et al. on Mar. 15, 1977; grain refinement as disclosed in U.S. Pat. No. 4,142,918, issued to J. T. Plewes on Mar. 6, 1979; and free machining as disclosed in U.S. Pat. No. 4,130,421, issued to J. T. Plewes et al. on Dec. 19, 1978. Also relevant in this context is a method for developing mechanical properties in certain quaternary Cu-Ni-Sn alloys which involves little or no cold working as disclosed by J. T. Plewes in patent application Ser. No. 6,616, filed Jan. 10, 1979, U.S. Pat. No. 4,260,432.
According to references cited above, development of a preferred spinodal structure and concomitant high levels of strength and ductility in Cu-Ni-Sn alloys is effected by processing involving cold working or by the addition of refractory elements or iron. The latter approach is effective even in the absence of cold work and has been preferred where articles are shaped as cast or where shaping is at elevated temperatures as, e.g., when shaping is by forging or extruding. Fabrication of alloys comprising refractory components may, however, require special care, e.g., in the preparation of a melt. Consequently, means are desired for producing shaped articles of Cu-Ni-Sn spinodal alloys without required cold working and without required refractory additives.
Also considered were U.S. Pat. No. 3,941,620, issued to M. J. Pryor et al. on Mar. 2, 1976 and U.S. Pat. No. 4,046,596, issued to R. T. Metcalfe et al. on Sept. 6, 1977. These patents disclose Cu-Ni-Sn alloys prepared by methods which rely on solution heat treatment at a temperature corresponding to a single phase state prior to rapid cooling, cold working, and aging.